To be sure, Senator Rubio can hone his answers and he can expand his talking points. But the underlying charge by New Jersey Gov. Chris Christie at the debate remains: Is the Floridian simply too inexperienced for the presidency? Is he just like another first-term senator – Barack Obama – who decided to run for president?

In the year of the political outsider, it’s not clear how much that matters to voters. But it’s a relevant question, given the persistent criticism that Mr. Obama has not understood how to get things done in Washington.

“There are certainly people who believe that maybe Obama didn’t have enough experience,” says Jennifer Duffy of the independent Cook Political Report.

But elements of Rubio's résumé could help the senator stave off claims of inexperience.

For one, Rubio has worked hard to establish his credentials in the area of foreign policy – a key hole for most young politicians. In addition, Rubio has legislative experience as the former speaker of the Florida House of Representatives – giving him hands-on practice in how to work with legislators.

Rubio’s supporters are quick to point out these distinctions.

Rubio “has a lot more experience than Obama did when he got involved in this. You gotta keep in mind, when a guy is speaker of the house of a major state, that’s a big deal,” says Sen. Jim Inhofe (R) of Oklahoma, who has been in Congress for 30 years and has endorsed Rubio.

While Obama served seven years in the Illinois Senate, co-chairing one committee and chairing another, Rubio has called him a “back-bencher.”

But Rubio’s success at the head of the Florida House was mixed.

On the day he was designated speaker, he asked lawmakers to look in their desks. There they found a book titled “100 Innovative Ideas for Florida’s Future.” Its pages were blank, to be filled with future legislation. The book became the core of his speakership.

While many ideas were realized (multiyear car registration, for example, and expanded school vouchers), the boldest idea – replacing property taxes with a consumption tax – was not.

Rubio battled over property taxes with the Florida Senate and with then-Republican Gov. Charlie Crist, whom he later pummeled in the race for US Senate.

Since his election to the Senate in 2010, Rubio has carved out foreign affairs and national security as his specialty, serving on both the foreign affairs and intelligence committees. He’s tried to make himself the standout foreign-policy candidate in the Republican field, sounding particularly tough on terrorism – a top issue for voters – and on China and Iran.

Foreign affairs featured heavily in the Obama campaign of 2008, as he promised to quickly end the Iraq War and to ramp up forces in Afghanistan. Then-Senator Obama served on the foreign affairs and homeland security committees.

But Rubio and his allies are more conspicuously playing up his foreign policy credentials as an asset. “The best experience he will bring, I think, is his knowledge. …He has the trust and the knowledge to keep this country safe,” Sen. Deb Fischer (R) of Nebraska, who serves on the Senate Armed Services Committee, told the Monitor this week. She recently endorsed Rubio.

Even Democratic Sen. Robert Menendez of New Jersey, the former chair of the foreign relations committee, acknowledges that Rubio “is definitely among the best” in foreign-affairs experience when considering the Republican field of candidates.

In a brief interview, he praised Rubio for their work together on sanctions against Venezuela for human rights abuses and on the issue of human trafficking. Senator Menendez said he wasn’t in a position to compare Rubio with Obama at this stage in the president’s political career, although the two Democrats served together on the foreign affairs committee.

Rubio and Menendez also worked together in the “gang of eight” to pass a comprehensive immigration reform bill in the Senate. Rubio has since walked back from that bill.

Rubio’s experience in state politics and his foreign affairs chops still don’t add up to presidential material, in the eyes of some of his colleagues. They just can’t get past the first-term-Obama comparison.

“We now have had experience with a president who had very little government experience before being elected president. We have an extraordinarily complex government to be run, and experience counts in government as it does in any other field,” says Sen. Susan Collins (R) of Maine, a moderate who just campaigned with Jeb Bush in New Hampshire.

“We have some very gifted individuals who are running who are first-term senators,” she added, meaning Rubio and Sen. Ted Cruz (R) of Texas. “But I am concerned about whether they have the knowledge base and experience to be effective.”

In the end, that may not matter. Republican voters are putting fresh ideas ahead of experience in this campaign. A Pew survey in October showed 65 percent of Republican and Republican-leaning registered voters felt it was more important that a candidate have new ideas than “experience and a proven record.”

But with Rubio hoping to follow Obama, the experience question does linger. Before Obama, “it was a bit of a theoretical question because there was no precedent,” says Ms. Duffy of the Cook Political Report. “But Rubio’s challenge now is that there is precedent.”